Zooplankton grazing of microplastic can accelerate global loss of ocean oxygen

Global warming has driven a loss of dissolved oxygen in the ocean in recent decades. Wedemonstrate the potential for an additional anthropogenic driver of deoxygenation, in whichzooplankton consumption of microplastic reduces the grazing on primary producers. Inregions where primary production is not limited by macronutrient availability, the reduction ofgrazing pressure on primary producers causes export production to increase. Consequently,organic particle remineralisation in these regions increases. Employing a comprehensiveEarth system model of intermediate complexity, we estimate this additional remineralisationcould decrease water column oxygen inventory by as much as 10% in the North Pacific andaccelerate global oxygen inventory loss by an extra 0.2-0.5% relative to 1960 values by theyear 2020. Although significant uncertainty accompanies these estimates, the potential forphysical pollution to have a globally significant biogeochemical signal that exacerbates theconsequences of climate warming is a novel feedback not yet considered in climate research.